Play-eliminating setting apparatus

ABSTRACT

The rotary pointer, and also a diagram carrier of an indicating and recording apparatus, are driven in a forward direction from a motor through a gear train having two branch gear trains. When the device is manually set in forward direction, play is introduced into the gear trains which is eliminated by biasing means loaded by the gear train during forward movement. During continuous setting in the rearward direction, the biasing means would be untensioned which is prevented by one-way blocking means. A lost-motion device permits rearward setting for an angle of over 180*, and then couples the gear train with the blocking means so that the gear train is blocked after limited rearward setting which negligibly untensions the biasing means.

United S ,ta tje "s Patent- 3,636,790 Bertranget al-. [45 1 Jan. 25, 1972 [54] PLAY-ELIMINATING 3,359,819 12/1967 Veillette et al. ..74/409 APPARATUS Primary ExqminerLeonard l-l. Gerin [72] Inventors: Hermann Bertrang; Horst Spormann, both Attorney-Michael S. Striker of Villingen, Germany [73] Assignee: Klenzle Applrate Gmbll, Villin- [57] ABSTRACT gen, Black forest, German The rotary pointer, and also a diagram carrier of an indicating m v W T and recording apparatus, are driven in a forward direction [22] 1970 from a motor through a gear train having two branch gear [2 A l N 84,060 trains. When the device is manually set in forward direction, play is introduced into the gear trains which is eliminated by I biasing means loaded by the gear train during forward move- [30] Ruth Appnnfion Priority ment. During continuous setting in the rearward direction, the Oct. 25, 1969 Germany. ..G 69 41 650.8 biasing means would he untensioned which is Prevented y one-way blocking means. A lost-motion device permits rear- [521 0.8. CI. ..74/409, 346/20 ward for ah angle of 180, and couples the [5]] IMOCL 17 55l18G01d9/QQ gear train with the blocking means so that the gear train is 581 Field olSeu-ch ..74/409; 346/20 blocked after limited rearward Setting which negligibly sions the biasing means. [56] Rafa-en Cited 10 Claims, 3 Drawing Figures UNITED STATES PATENTS 3,365,723 1/1968 Spormann ..74/409 X mzmmmzsmz 3.636790 SHEET 1 OF 2 Mfmms I 6? Spamann Hermam Bertranq PATENTED Jmzslszz 36353 sum 2 or 2 INVEN'IORS Horst Sporrnann Hermann Bertrang PLAY-ELIMINATING SETTING APPARATUS BACKGROUND OF THE INVENTION When the pointer, or diagram carrier, of a recording instrument is driven by a motor, such as a spring motor through a gear train always in forward direction, the play of the gear train is ineffective. However, when the indicator or diagram carrier has to be set to a new position by manual operation, and when the setting is carried out in the same forward direction in which the indicator and diagram carrier are driven, play is introduced into the gear train so that the following indication under the control of the drive means is not accurate. This is a particularly disturbing if between the drive motor and the diagram carrier, a long gear train is provided consisting of many meshing gears. The problem is even more complicated if in addition tothe diagram carrier, or a roller for a diagram band, also a time-indicating pointer has to be driven.

When by setting'in the forward direction, substantial play is introduced into the long gear train, time errors up to minutes may occur in the indication. Consequently, after a setting in the forward direction, it is necessary to eliminate the play, and only then can the diagram carrier or indicating pointer be driven again from the drive means. Particularly if the play in the gear train branch connecting the drive means with the diagram carrier, and in the gear train branch connecting the drive means with the indicating pointer, is different, synchronism between the pointer indication and the graphical recording on the diagram carrier is not assured.

The US. Pat. No. 3,105,731 discloses a setting apparatus for interconnected indicators in which the play introduced by forward setting is eliminated by a biasing means which includes a spring housing meshing with the gear of the gear train, and a spiral spring sliding on an inner surface of the spring housing. During rotation of the spring housing with the gear train in the forward direction, the spring is tensioned, and after the setting has introduced play into the gear train, all gears of the gear train are turned by the spring and spring housing in the opposite direction so that the play is eliminated.

- The arrangement has the disadvantage that, if the indicating pointer is set in a rearward direction, the spring housing is turned rearward with the spring which is untensioned so that the spring device is no longer effective to eliminate the play from the gear train after a repeated setting in the forward direction. To overcome this disadvantage, the US. Pat. No. 3,105,73l provides a setting control means which permits a rearward setting for an angle of substantially 60, corresponding to 2 hours of the indication by the pointer. After the angular displacement of 60, further turning is blocked by a projecting portion of an interrupted gear. If the users of the device do not understand the technical reason for the arrangement, they always try to set the device rearward, and to overcome the lock which causes damage to the apparatus. Generally, a user has the tendency to set the device rearward if this can be accomplished by turning over an angle of less then l80, since if the angle is greater, setting in the forward direction requires turning of the device through a smaller angle of less then 180.

SUMMARY OF THE INVENTION It is one object of the invention to overcome the disadvantages of the device disclosed in the U.S. Pat. No. 3,l05,73 l and to provide an apparatus which can not only be set in forward direction, but also in rearward direction for a sufficiently great angle permitted reasonable rearward setting without completely untensioning the biasing device by which play is eliminated after forward setting.

Another object of the invention is to provide a play eliminating setting apparatus of the above-described type, which can be set in rearward direction an angle of almost 360.

Another object of the invention is to connect the gear train by lost-motion means with blocking means so that rearward setting of the indicating pointer or diagram carrier for an angle of almost 360 is possible before the blocking means becomes effective.

With these objects in view, an embodiment of the invention comprises rotary means, such as a diagram carrier support and a pointer indicating time, a gear train driven by drive means and rotating the rotary means always in the same forward.

direction; setting means connectedwith a rotary means for turning the same in the forward direction, and also in rearward direction, whereby play is introduced'into the gear train during setting of the rotary means in the forward direction only; biasing means, preferably including a spring housing and a spiral spring frictionally connected with the spring housing, operatively connected, preferably by a gear on the housing, with the gear train so as to be loaded during rotation of the rotary means in the forward direction and being gradually untensioned during rearward setting; one-way blocking means preferably including a ratchet wheel and an escapementpawl, for blocking rotation of the gear train with the rotary means only in the rearward direction; and lost-motion means between the blocking means and the gear train, and preferably including a pin and a slot, permitting rearward setting of the rotary means with the gear train for a predetermined angle, preferably almost 360", before the blocking means blocks the gear train and thereby the setting means so that complete untensioning of the biasing means by continued rearward setting is prevented.

Preferably, the pin is secured to the spring housing and pro} 3 jects into a part-circular slot in the ratchet wheel.

jects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side view, partially in section, illustrating an apparatus in accordance with the invention;

FIG. 2 is a fragmentary perspective view, illustrating'a blocking means combined with a'lost-motion device used in the apparatus of FIG. I; and

FIG. 3 is a cross-sectional view taken on'line A-A in FIG. 1, and illustrating the biasing means by which play is eliminated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus is disclosed as embodied in a tachograph in which the driving clockwork for a diagram carrier support is mounted in a pivoted lid or cover on whose inner face, the diagram carrier support is arranged, while the outer face has a transparent cover behind which pointers indicate the time and speed measured by the tachograph. However, it will be understood that the apparatus of the invention can be applied to any type of driving mechanism for diagram carriers or pointers, or for a transporting wheel transporting a record carrier tape or band.

Behind a fixed cover plate 1, the gear mechanism is mounted between two thin supporting plates 2 and 3. The drive means include an electronic pulse generator, or a regulated electric motor of constant rotary speed, or a spring motor with a regulating escapement mechanism, not shown. Any of these drive motors can be used for driving the coupling part 4 shown in FIG. 1 which is fixedly secured to a shaft 5 whose ends are mounted in bearings of walls 2 and 3, as are the ends of all other shafts which will be described hereinafter. A pinion 6 is secured to part 4, and meshes with a gear 7 mounted on a shaft 8 which further carries a gear 9 meshing with a gear 10 which is mounted on a shaft 11. Shaft I l carries the pinion 12 which meshes with gear 13, which is secured to shaft 14 and connected by a friction coupling 15 on the one hand with a gear 16 and'on the other hand with a gear 17. Gears 16 and 17 are the first gears of two branched gear trains. Gear 16 serves for driving the diagram carrier support 18 through the meshing gears 19, 20, and 21, while gear 17 drives through meshing gears 22, 23 the minute pointer 23b and through gears 24, 25 an hour pointer 25b, respectively mounted on the hollow shaft 230 and 25a. The pointers, not shown, move over a dial 26 which indicates the hours and minutes.

Setting means are provided and include a knurled knob secured to a pinion 29 meshing with a gear 28 which meshes with another setting gear 27 meshing with gear 23 for setting the minute pointer which is followed by the hour pointer.

Since diagram carrier support 18 is connected by gears 21, 20, l9, l6, 17, 22 with gear 23, the diagram carrier support 18 is set together with the minute pointer, but of course at a different speed since the diagram carrier support 18 turns one revolution in 24 hours, and rotates at half the speed of the hour pointer.

, When the pointers are set by the setting means 27 to 30 i the forward direction, to an exact time, play is introduced into the gear train between gear 23 and pinion 6, but since gears 17 and 16 are also connected by shaft 14, also into the branch gear train l6, 19, 20, 21. Consequently after setting of the pointers and diagram carrier in forward direction, it is necessary to eliminate the play in the gear train before the diagram carrier support 18 and the pointers are driven from the drive means 4.

Gear 21 which is connected with the diagram carrier support 18, meshes with a biasing gear 33 provided on the outside of a cylindrical spring housing 31 which is best seen in FIGS. 2 and 3. As particularly shown in FIG. 3, the spring housing 31 is a wheel and has an outer wall 34 provided on the outside with the gear teeth 33, and on the inside with a smooth cylindrical surface on which the end portion 36 of a spiral spring slidingly rests. The inner end of spring 35 is secured to a fixed shaft 32 which has a flat portions for securing the end of the spring. Fixed shaft 32 is fixedly secured to the walls 2 and 3. Gear 21, which drives the diagram carrier support 18, meshes with biasing gear 33 and also drives the spring housing 31 in a forward direction corresponding to the forward movement of the pointers and diagram carrier. The phrase forward direction" is used in this application to denote a direction of rotation causing forward movements of the pointer and diagram carrier irrespective of whether individual rotary members rotate in clockwise or counterclockwise direction.

Before the biasing means shown in FIG. 3 is assembled with the other parts, the spiral spring 35 is in the position of FIG. 3. When the apparatuls is assembled, and the drive means drive by a first gear train branch starting with gear 16 the diagram carrier support 18, the spring housing 33 is driven by gear 21 in counterclockwise direction, as indicated by the arrow B, so that the spring is tensioned while the outer end 36 remains in frictional engagement at the original face portion of the inner surface of wall 34. In other words, when the spring housing 31 turns in clockwise direction, the end portion 36 of spring 35 turns the same angle in clockwise direction so that the spring is tensioned. However, at a'predetermined tension of spring 35, the spring is not further tensioned, and the end portion 36 begins to slide on the inner surface of the spring housing which continues its rotation. In this manner, spring 35 is tensioned, and is capableof turning the diagram carrier support 18, and the shaft portions 23a, 25a with the pointers through gears 33, 21, 20, 19, 16, 17, 22, 23, 24, and 25 in the opposite direction than during driving by the drive means so that no play is left in the gear train between the drive means 4 and record carrier support 18 and the pointers, not shown. In other words, the tension of spring 35 is opposite to the forward direction of rotation which is indicated by the arrows C in FIG. 2 which shows the gear 21 meshing with the gear 33 of the spring housing 31.

The pin 37 is secured to the top wall of the spring housing 31 and projects into an almost circular .slot 38 in a ratchet wheel 39. v

It is also possible to reverse the arrangement and to secure the pin to the ratchet wheel 39, while providing the slot 38 in the spring housing 31. Slot 38 and pin'37 constitute a lost-motion means connecting the spring housing 31 with the ratchet wheel 39. Slot 38 has the form of a part-circular groove on the inner face of the top wall of spring housing 31, and extends almost over 360. Ratchet wheel and spring housing 31 with the biasing gear 33 are both mounted for rotation on the stationary shaft 32 to which the inner end of spring 35 is secured. A stationary journal 41 on wall 2 supports an escapement pawl 42 with two teeth 43 and 44 for angular movement, which controls turning movement of ratchet wheel 39, and permits the ratchet wheel to turn only in the forward direction indicated by the arrow B. During movement in this forward direction, the flat backs of the ratchet teeth slide under the pawl portion 43 and turn pawl 42 to a position in which pawl portion 44 engages the ratchet teeth. Turning of the ratchet wheel 39 in the rearward direction indicated by the arrow C is not possible since the steep flanks of the ratchet teeth engage portion 44 of pawl 42. However, spring housing 31 can turn al most -360 in the rearward direction indicated by the arrow C since the pin 37 moves in the slot 38 until blocked by the end of the slot which constitutes an abutment.

When the apparatus is assembled with the spring housing 31 and spring 35, pin 37 is located in slot 38 in the positionillustrated in FIG. 2, and the assembly is carried out in such a manner that spring 35 is already substantially pretensioned so that the tension of spring 35 is sufficient to turn the gears of the gear train to a position eliminating the play between the drive means and the pointers and record carrier support 18.

While theapparatus is driven by the drive means, and the gears of the gear train and the diagram carrier support 18 and the pointers rotate in forward direction, the spring housing turns in a direction B. As can be best seen in FIG. 3, this will result in further tensioning of spring 35. The ratchet wheel 39 of the one-way blocking means 39, 42, 43, 44 does not turn at first in the clockwise direction of the arrow B, since pin turning in the slot 38 of ratchet wheel 39 moves from one end of the slot to the other until abutting the end of the slot in a posi tion which is not shown. From now on, the spring housing 31 is coupled by'the lost-motion means 37, 38 with the blocking ratchet wheel 39, and the same turns also in the direction B with pawl 42 performing an oscillating movement since pawl 42 is displaced by each tooth of the blocking wheel 39.

The driving of the diagram carrying support 18 in the forward direction of the arrow B will not influence the position of the pin 37 at the end of the slot 38, and the pin remains in the end position at the end of the slot opposite to the end at which pin 37 is shown in FIG. 2. During setting of the pointers, not shown, on shaft portions 25a and 23a, by the setting means 27 to 30 acting on gear 23, in forward direction, the spring housing 31 with gear 33, and the blocking ratchet wheel 39 remain in the same coupled position. After termination of the setting operation, the tension of spiral spring 35 acts on spring housing 31 and biasing gear 33 on gear 21, and consequently on all gears between gear 21 and the diagram carrier support 18 and shaft portions 231:, 25a, to turn in the rearward direction of the arrow C so that the play introduced into the gear train by the setting operation is eliminated so that the diagram carrier support 18 and the pointers can be driven from the drive means 4 without play.

During this operation of the biasing means 31, 33, 35, 32, pin 37 moves a small distance corresponding to the play in the gear train in slot 38 while blocking wheel 39 is locked by pawl end portion 44 of pawl 42.

During setting in the opposite rearward direction, no play is introduced into the gear train. Gear 21 and thereby biasing gear 33 are driven by the setting means in the rearward direction C, while pin 37 of the lost-motion means 37, 38, travels from the end position in which it was before, to the end position shown in FIG. 2, while pawl 42 blocks the blocking ratchet wheel 39. When pin 37 arrives at the abutment formed by the end of slot 38 in the position of FIG. 2, it is not possible to turn the setting means and particularly knob 30 further in the rearward'direction, and the setting means is blocked since gear 21, gear 33, and spring housing 31'are blocked since they are coupled to the one-way blocking means 42, 39 by the lostmotion device 37, 38.

The turning movement of the spring housing 33 for almost one revolution in the rearward direction has slightly untensioned the'spring but sufficient force. is accumulated in the spring so that, if the rearward setting is directly followed a perhaps short forward setting, play is again introduced into the gear train, the spring 37 and spring housing 33 can again eliminate the play, as described above following a forwardsetting operation. 1

The transmission ratio between the gear 21 and the spring housing 31 .with gear 33 is so selected that the diagram carrier support can be set almost one complete revolution in the rearward direction, which means that the pointers can be turned almost two complete revolutions, since the ratio between the diagram carrier support 18 and the hour pointer is 2:1. This situation will practically never occur, since it is customary to set pointers in such a manner that the shortest angular displacement is used. For example, it will be preferred to turn the pointer in forward direction to the indication 5 o'clock which is less than 180, to turning the pointer in the rearward direction to the position which requires turning of more than 180. However, the apparatus of the invention permits a rearward turning through almost one complete revolution before the setting means is blocked, and that is sufficient to assure a foolproof operation.

From the above description it will become apparent that the present invention provides an apparatus which permits setting in forward and rearward direction, without completely exhausting the spring force required for eliminating play introduced into the gear train during a setting operation.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of play-eliminating setting apparatus, differing from the types described above.

While the invention has been illustrated and described as embodied in a setting apparatus for clock pointers and diagram carriers eliminating play in the drive gear train and perrnitting limitedsetting in rearward direction, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore,v such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Lettera Patent is set forth in the appended claims.

We claim: l. Play-eliminating setting apparatus, comprising drive means; rotary means; a gear train connecting said drive means with said rotary means for turning the same always in the same forward direction so that no play is efi'ective in said forward direction; setting means connected with said rotary means for turning the same in said forward direction, and also in rearward direction whereby play is introduced into said gear train during setting of said rotary means in said forward direction only; rotary biasing means operatively connected with said gear train so as to be loaded during rotation of said rotary means in said forward direction and being gradually untensioned during rearward setting; one-way blocking means for blocking rotation only in said rearward direction; and lost-motion means between said blocking means and said biasing blocking means blocks said biasing means and thereby said gear train and said setting means so that complete untensioning of said biasing means by continued rearward setting is prevented.

2. Apparatus as claimed in claim 1 wherein said one-way blocking means include a rotary ratchet wheel, and an escapement pawl cooperating with said ratchet wheel.

3. Apparatus as claimed in claim 1 wherein said lost-motion means includes a part-circular slot, wherein the ends of said slot are said abutment means, and are spaced from each other an angle of at least and wherein said stop is a pin located in said slot.

4. Apparatus as claimed in claim 3 wherein said part-circular slot extends through an angle of almost 360.

5. Apparatus as claimed in claim 1 wherein said one-way blocking means include a rotary ratchet wheel, and an escapement pawl cooperating with said ratchet wheel and blocking movement of the same only in said rearward direction; wherein said ratchet wheel is formed with a part-circular slot having ends forming said abutment means; wherein said stop is a pin in said slot; and wherein said biasing means include a biasing gear meshing with said gear train and carrying said pin.

6. Apparatus as claimed in claim 1 wherein said biasing means include a rotary spring housing wheel having an outer biasing gear meshing with said gear train and an inner friction surface, and a spiral spring in said spring housing wheel having an inner fixed end and an outer end slidingly engaging said friction surface so that said spiral spring is tensioned during rotation of said gear train and of said rotary means with said spring housing wheel in said forward direction, and untensioned during rotation in said rearward direction; and wherein said lost-motion means connects said spring housing wheel and biasing gear with said one-way blocking means.

7. Apparatus as claimed in claim 6 wherein the transmission ratio between said biasing gear and said gear train is selected so that said rotary means makes almost one revolution in said rearward direction before said lost-motion means moves to an end position in which said blocking means blocks rotation of said spring housing wheel in said rearward direction.

8. Apparatus as claimed in claim 6 wherein said blocking means includes a rotary ratchet wheel, and an cscapement pawl cooperating with said ratchet wheel and blocking movement of the same only in said rearward direction; comprising a shaft supporting said spring housing wheel, biasing gear, and ratchet wheel for rotation about a common axis, and being secured to said spiral spring; and wherein said lost-motion means include a part-circular slot in one of said wheels concentric with the axis of said shaft and having said abutment means, said stop being a pin secured to the other of said wheels and coupling in one end position at one end of said slot said wheels for turning movement so that rearward rotation of said other wheel is blocked in said end position.

9. Apparatus as claimed in claim 8 wherein said one wheel is said ratchet wheel and is formed with said slot; wherein said other wheel is said spring housing wheel; and wherein said slot extends in said ratchet wheel over an arc greater than 180 and less than 360.

10. Apparatus as claimed in claim 6 wherein said rotary means include a rotary diagram carrier and a rotary pointer; wherein said gear train includes a first branch gear train connecting said drive means with said diagram carrier, and a second branch gear train connecting said drive means with said rotary pointer; wherein said setting means includes a setting gear meshing with said second branch gear train; and wherein said biasing gear meshes with said first branch gear train. 

1. Play-eliminating setting apparatus, comprising drive means; rotary means; a gear train connecting said drive means with said rotary means for turning the same always in the same forward direction so that no play is effective in said forward direction; setting means connected with said rotary means for turning the same in said forward direction, and also in rearward direction whereby play is introduced into said gear train during setting of said rotary means in said forward direction only; rotary biasing means operatively connected with said gear train so as to be loaded during rotation of said rotary means in said forward direction and being gradually untensioned during rearward setting; one-way blocking means for blocking rotation only in said rearward direction; and lost-motion means between said blocking means and said biasing means and including a stop and abutment means for the same permitting rearward setting of said rotary means with said gear train and biasing means for a predetermined angle before said blocking means blocks said biasing means and thereby said gear train and said setting means so that complete untensioning of said biasing means by continued rearward setting is prevented.
 2. Apparatus as claimed in claim 1 wherein said one-way blocking means include a rotary ratchet wheel, and an escapement pawl cooperating with said ratchet wheel.
 3. Apparatus as claimed in claim 1 wherein said lost-motion means includes a part-circular slot, wherein the ends of said slot are said abutment means, and are spaced from each other an angle of at least 180*; and wherein said stop is a pin located in said slot.
 4. Apparatus as claimed in claim 3 wherein said part-circular slot extends through an angle of almost 360*.
 5. Apparatus as claimed in claim 1 wherein said one-way blocking means include a rotary ratchet wheel, and an escapement pawl cooperating with said ratchet wheel and blocking movement of the same only in said rearward direction; wherein said ratchet wheel is formed with a part-circular slot having ends forming said abutment means; wherein said stop is a pin in said slot; and wherein said biasing means include a biasing gear meshing with said gear train and carrying said pin.
 6. Apparatus as claimed in claim 1 wherein said biasing means include a rotary spring housing wheel having an outer biasing gear meshing with said gear train and an inner friction surface, and a spiral spring in said spring housing wheel having an inner fixed end and an outer end slidingly engaging said friction suRface so that said spiral spring is tensioned during rotation of said gear train and of said rotary means with said spring housing wheel in said forward direction, and untensioned during rotation in said rearward direction; and wherein said lost-motion means connects said spring housing wheel and biasing gear with said one-way blocking means.
 7. Apparatus as claimed in claim 6 wherein the transmission ratio between said biasing gear and said gear train is selected so that said rotary means makes almost one revolution in said rearward direction before said lost-motion means moves to an end position in which said blocking means blocks rotation of said spring housing wheel in said rearward direction.
 8. Apparatus as claimed in claim 6 wherein said blocking means includes a rotary ratchet wheel, and an escapement pawl cooperating with said ratchet wheel and blocking movement of the same only in said rearward direction; comprising a shaft supporting said spring housing wheel, biasing gear, and ratchet wheel for rotation about a common axis, and being secured to said spiral spring; and wherein said lost-motion means include a part-circular slot in one of said wheels concentric with the axis of said shaft and having said abutment means, said stop being a pin secured to the other of said wheels and coupling in one end position at one end of said slot said wheels for turning movement so that rearward rotation of said other wheel is blocked in said end position.
 9. Apparatus as claimed in claim 8 wherein said one wheel is said ratchet wheel and is formed with said slot; wherein said other wheel is said spring housing wheel; and wherein said slot extends in said ratchet wheel over an arc greater than 180* and less than 360*.
 10. Apparatus as claimed in claim 6 wherein said rotary means include a rotary diagram carrier and a rotary pointer; wherein said gear train includes a first branch gear train connecting said drive means with said diagram carrier, and a second branch gear train connecting said drive means with said rotary pointer; wherein said setting means includes a setting gear meshing with said second branch gear train; and wherein said biasing gear meshes with said first branch gear train. 